Expandable introducer sheath

ABSTRACT

An introducer sheath has a radially unexpanded and a radially expanded configuration, where the sheath locally expands from the unexpanded configuration to the expanded configuration when a device is advanced through a lumen thereof, and locally contracts back to the unexpanded configuration after the device advances past that location. Embodiments of the introducer sheath include an outer tubular layer comprising a longitudinal cut therethrough, and an inner tubular layer comprising at least one pleat extending through the longitudinal cut to an outside surface of the outer tubular layer. Embodiments of the inner tubular layer are adhered to an inner surface of the outer tubular layer, with the pleat not adhered to an outer surface of the outer tubular layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/249,867, filed Oct. 10, 2008, now U.S. Pat. No. 8,690,936, the entiredisclosure of which is incorporated by reference.

FIELD

The present application concerns embodiments of a sheath for use withcatheter-based technologies for repairing and/or replacing heart valves,as well as for delivering a prosthetic device, such as a prostheticvalve to a heart via the patient's vasculature.

BACKGROUND

Endovascular delivery catheter assemblies are used to implant prostheticdevices, such as a prosthetic valve, at locations inside the body thatare not readily accessible by surgery or where access without invasivesurgery is desirable. For example, aortic, mitral, tricuspid, and/orpulmonary prosthetic valves can be delivered to a treatment site usingminimally invasive surgical techniques.

An introducer sheath can be used to safely introduce a deliveryapparatus into a patient's vasculature (e.g., the femoral artery). Anintroducer sheath generally has an elongated sleeve that is insertedinto the vasculature and a housing that contains one or more sealingvalves that allow a delivery apparatus to be placed in fluidcommunication with the vasculature with minimal blood loss. Aconventional introducer sheath typically requires a tubular loader to beinserted through the seals in the housing to provide an unobstructedpath through the housing for a valve mounted on a balloon catheter. Aconventional loader extends from the proximal end of the introducersheath, and therefore decreases the available working length of thedelivery apparatus that can be inserted through the sheath and into thebody.

Conventional methods of accessing a vessel, such as a femoral artery,prior to introducing the delivery system include dilating the vesselusing multiple dilators or sheaths that progressively increase indiameter. This repeated insertion and vessel dilation can increase theamount of time the procedure takes, as well as the risk of damage to thevessel.

Radially expanding intravascular sheaths have been disclosed. Suchsheaths tend to have complex mechanisms, such as ratcheting mechanismsthat maintain the shaft or sheath in an expanded configuration once adevice with a larger diameter than the sheath's original diameter isintroduced.

However, delivery and/or removal of prosthetic devices and othermaterial to or from a patient still poses a significant risk to thepatient. Furthermore, accessing the vessel remains a challenge due tothe relatively large profile of the delivery system that can causelongitudinal and radial tearing of the vessel during insertion. Thedelivery system can additionally dislodge calcified plaque within thevessels, posing an additional risk of clots caused by the dislodgedplaque.

Accordingly, there remains a need in the art for an improved introducersheath for endovascular systems used for implanting valves and otherprosthetic devices.

SUMMARY

Embodiments of the present expandable sheath can minimize trauma to thevessel by allowing for temporary expansion of a portion of theintroducer sheath to accommodate a delivery system, followed by a returnto the original diameter once the delivery system passes through. Someembodiments can comprise a sheath with a smaller profile than that ofprior art introducer sheaths. Furthermore, certain embodiments canreduce the length of time a procedure takes, as well as reduce the riskof a longitudinal or radial vessel tear, or plaque dislodgement becauseonly one sheath is required, rather than several different sizes ofsheaths. Embodiments of the present expandable sheath can require only asingle vessel insertion, as opposed to requiring multiple insertions forthe dilation of the vessel.

One embodiment of a sheath for introducing a prosthetic device comprisesan inner tubular layer, an outer tubular layer, and an intermediatetubular layer disposed between the inner and outer tubular layers. Atleast a portion of the sheath can be designed or configured to locallyexpand from a first diameter to a second diameter as the prostheticdevice is pushed through a lumen of the sheath, and then at leastpartially return to the first diameter once the prosthetic device haspassed through.

The inner tubular layer can comprise polytetrafluoroethylene (PTFE),polyimide, polyetheretherketone (PEEK), polyurethane, nylon,polyethylene, polyamide, or combinations thereof. The intermediatetubular layer can comprise Nitinol, stainless steel, cobalt chromium,spectra fiber, polyethylene fiber, aramid fiber, or combinationsthereof. The outer tubular layer can comprise PTFE, polyimide, PEEK,polyurethane, nylon, polyethylene, polyamide, polyether block amides,polyether block ester copolymer, thermoset silicone, latex,poly-isoprene rubbers, or combinations thereof.

Disclosed embodiments of a sheath comprise a proximal and a distal endopposite one another, and a hemostasis valve at or near the proximal endof the sheath. In some embodiments, the outer diameter of the sheathdecreases along a gradient from the proximal end to the distal end ofthe sheath.

Some embodiments of a sheath for introducing a prosthetic devicecomprise an outer tubular layer, at least a portion of which is adaptedto split along its length as the prosthetic device passes through thelumen to facilitate expansion of the sheath. Alternatively, or inaddition to, some embodiments of a sheath comprise an inner tubularlayer, at least a portion of which is adapted to split along its lengthas the prosthetic device passes through the lumen to facilitate radialexpansion of the sheath. In some embodiments, the inner tubular layerand/or the outer tubular layer comprises a longitudinal cut or notchalong at least a portion of its length.

Disclosed embodiments of a sheath for introducing a prosthetic devicecomprise an outer covering disposed on the outer surface of the outertubular layer. In some embodiments, the outer covering is removableand/or adapted to split along at least a portion of its length tofacilitate radial expansion of the sheath. For example, the outercovering can be provided with peel tabs to facilitate splitting and/orsliding the outer covering off of the underlying sheath once a portionof the sheath is inserted into a patient's vessel.

The intermediate tubular layer is discontinuous in some embodiments. Forexample, the intermediate tubular layer can comprise a mesh structurehaving at least two sections spaced apart from each other along alongitudinal axis parallel to the lumen of the sheath. In suchembodiments, each section can be connected by at least one strut to anadjacent section. Similarly, embodiments of a sheath can comprise aninner tubular layer with at least one discontinuous section along itslongitudinal axis to facilitate radial expansion of the inner tubularlayer. In some embodiments, the intermediate layer is self-expandable.

Additionally, disclosed embodiments can further comprise a lubricatingliner on at least a portion of the inner surface of the inner tubularlayer and/or an exterior hydrophilic coating on at least a portion ofthe outer surface of the outer tubular layer. Sheaths can also compriseat least one radiopaque filler and/or marker, such as barium sulfite,bismuth trioxide, titanium dioxide, bismuth subcarbonate, orcombinations thereof.

Some embodiments of a sheath for introducing a prosthetic device into apatient's vasculature comprise an inner tubular layer, an outercovering, and a self-expanding intermediate tubular layer disposedbetween the inner tubular layer and the outer covering. The outercovering can be adapted to maintain the self-expanding intermediatetubular layer in a crimped state having a first diameter, wherein theouter covering is at least partially moveable along the length of thesheath or removable from the sheath once the sheath is at leastpartially inserted into the patient's vasculature, to allow forself-expansion of the intermediate tubular layer to an expanded statehaving a second diameter greater than the first diameter. In someembodiments, the sheath is adapted to at least partially compresstowards the first diameter upon removal of the sheath from the patient'svasculature. To facilitate moving or removing the outer covering fromthe sheath, some embodiments comprise an outer covering provided with atleast one peel tab.

Some embodiments of a sheath comprise an inner tubular layer and anouter tubular layer, where the outer tubular layer includes at least onelongitudinal cut through it such that the outer tubular layer comprisesa first longitudinal edge, a second longitudinal edge, and a gap therebetween, wherein the inner tubular layer is associated with an innersurface of the outer tubular layer, and wherein a portion of the innertubular layer extends through the gap.

In some embodiments, the portion of the inner tubular layer that extendsthrough the gap forms a folded portion outside the outer tubular layer.

Some embodiments of a sheath also comprise an outer covering over atleast a portion of an outer surface of the outer tubular layer, whereinthe outer covering overlaps at least a portion of the folded portion ofthe inner tubular layer.

At least a portion of an outer surface of the inner tubular layer can besurface treated, etched, or otherwise modified. The inner tubular layerand the outer tubular layer can be adhesively secured to each othersubstantially only at the portion that is surface treated or etched, soas to substantially avoid interference with radial expansion of thesheath.

In some embodiments, the inner tubular layer comprises PTFE. In someembodiments, the outer tubular layer comprises high densitypolyethylene.

Methods of making a sheath are also disclosed. One method comprisesproviding a mandrel, mounting an inner layer on the mandrel such thatthe mandrel is positioned within a lumen formed by the inner layer,mounting an outer layer having a longitudinal cut on the inner layersuch that an excess portion of the inner layer extends through thelongitudinal cut, and forming a pleat or fold in the excess portion ofthe inner layer.

Another method of making a sheath comprises providing a mandrel andapplying an inner layer on the mandrel, such as by spray coating or dipcoating the mandrel. An intermediate layer can then be mounted on theinner layer. An outer layer can be applied over the intermediate layer,such as by a second spray coating or dip coating step.

Methods can comprise etching or surface treating at least a portion ofthe inner layer.

In some embodiments of methods of making a sheath, layers can bepre-formed and mounted on a mandrel, and then fused or thermally bondedtogether. For example, in one method, an inner layer is applied to amandrel. An intermediate layer can be applied to the outer surface ofthe inner layer. An outer layer can be applied to the outer surface ofthe intermediate layer. Heat shrink tubing can be applied, and theassembly heated, such that the inner layer, the intermediate layer,and/or the outer layer are thermally bonded and compressed togetherunder the heat shrink tubing.

In some embodiments of a method of making a sheath, a second mandrel isprovided. The second mandrel can be inserted within a second lumenformed by the excess portion of the inner layer.

Methods of making a sheath can comprise applying a radiopaque markerand/or filler to the inner and/or outer layer of the sheath, orembedding such markers and/or fillers within one or more of the innerand outer layers of the sheath.

In some methods, a partial slit or score line can be applied to thesheath. For example, a partial slit or score line can be cut in thesheath such that the score line extends from a point distal to aradiopaque marker to the distal tip of the sheath.

A sheath can also be provided with an over covering in some methods. Theouter covering can be associated with an outer surface of the outerlayer, such that at least a portion of the outer covering overlaps atleast a portion of the pleat or fold formed in the excess portion of theinner portion extending through the longitudinal cut in the outer layer.

Disclosed methods of introducing a prosthetic device into a patient'svasculature comprise positioning a expandable introducer sheath in apatient's vessel, wherein the expandable introducer sheath comprises aninner tubular layer and an outer tubular layer, wherein the outertubular layer contains a longitudinal cut through it such that the outertubular layer comprises a first longitudinal edge, a second longitudinaledge, and a gap there between, and wherein a portion of the innertubular layer extends through the gap, introducing the device into theexpandable introducer sheath, expanding a portion of the introducersheath via radial force applied by the device at the location of theexpanded portion, moving the device through the expanded portion, and atleast partially collapsing the expanded portion of the introducer sheathafter the device has passed through the expanded portion.

The foregoing and other features and advantages of the invention willbecome more apparent from the following detailed description, whichproceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view of a sheath according to the presentdisclosure along with an endovascular delivery apparatus for implantinga prosthetic valve.

FIGS. 2A, 2B, and 2D are section views of embodiments of a sheath forintroducing a prosthetic device into a patient, and FIG. 2C is aperspective view of one component of such a sheath.

FIG. 3 is an elevation view of the sheath shown in FIGS. 2A-2D.

FIGS. 4A-4B are elevation views of two embodiments of a sheath accordingto the present disclosure, having varying outer diameters.

FIG. 5 illustrates an elevation view of one embodiment of a sheath,expanded at a first location to accommodate a delivery system.

FIG. 6 shows an elevation view of the sheath of claim 5, expanded at asecond location, farther down the sheath.

FIG. 7 shows a section view of another embodiment of a sheath thatfurther comprises an outer covering or shell.

FIG. 8 illustrates an elevation view of one embodiment of a sheath withan outer covering or shell.

FIG. 9 illustrates a partial elevation view of one embodiment of anintermediate tubular layer that can be used to construct a sheathaccording to the present disclosure.

FIG. 10 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a variable diamond design.

FIG. 11 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a diamond design with spring struts.

FIG. 12 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a diamond design with straight struts.

FIG. 13 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a saw tooth design with spring struts.

FIG. 14 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a saw tooth design with straightstruts.

FIG. 15 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a diamond design with straight struts.

FIG. 16 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a helical or spiral design.

FIG. 17 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a diamond design with non-straightstruts.

FIG. 18 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having an alternative diamond design withnon-straight struts.

FIG. 19 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having yet another diamond design withnon-straight struts.

FIG. 20 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a diamond design with struts.

FIG. 21 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a design similar to that shown in FIG.20, but with additional struts.

FIG. 22 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a diamond design with spiral struts.

FIG. 23 illustrates a partial elevation view of another embodiment of anintermediate tubular layer having a diamond design with adjacent struts.

FIG. 24 illustrates a section view of one embodiment of a sheath havinga longitudinal notch.

FIG. 25 shows a section view of one embodiment of a sheath having alongitudinal cut in the inner layer.

FIG. 26 shows a perspective view of one embodiment of a sheath having aplurality of notches or cuts in the outer tubular layer.

FIG. 27A-27E illustrate a section view of one embodiment of a sheath,wherein the outer tubular layer contains a longitudinal cut, and theinner layer extends into the gap created by the cut in the outer tubularlayer, in an unexpanded configuration.

FIG. 28 shows a section view of the sheath of FIG. 27 in an expandedconfiguration.

FIGS. 29A-29D show section views of various embodiments of a sheathhaving overlapping sections.

FIG. 30 illustrates a block diagram of one embodiment of a method ofmaking a sheath according to the present disclosure.

FIG. 31 illustrates a block diagram of another embodiment of a method ofmaking a sheath according to the present disclosure.

FIGS. 32A-32H illustrate section or elevation views of various methodsteps of the methods shown in FIGS. 30-31.

FIG. 33 illustrates a plan view of one embodiment of a sheath having apartial slit or score line.

FIG. 34 illustrates a plan view of another embodiment of a sheath havinga partial slit or score line.

DETAILED DESCRIPTION

As used in this application and in the claims, the singular forms “a,”“an,” and “the” include the plural forms unless the context clearlydictates otherwise. Additionally, the term “includes” means “comprises.”Further, the terms “coupled” and “associated” generally meanselectrically, electromagnetically, and/or physically (e.g., mechanicallyor chemically) coupled or linked and does not exclude the presence ofintermediate elements between the coupled or associated items.

Although the operations of exemplary embodiments of the disclosed methodmay be described in a particular, sequential order for convenientpresentation, it should be understood that disclosed embodiments canencompass an order of operations other than the particular, sequentialorder disclosed. For example, operations described sequentially may insome cases be rearranged or performed concurrently. Further,descriptions and disclosures provided in association with one particularembodiment are not limited to that embodiment, and may be applied to anyembodiment disclosed.

Moreover, for the sake of simplicity, the attached figures may not showthe various ways (readily discernible, based on this disclosure, by oneof ordinary skill in the art) in which the disclosed system, method, andapparatus can be used in combination with other systems, methods, andapparatuses. Additionally, the description sometimes uses terms such as“produce” and “provide” to describe the disclosed method. These termsare high-level abstractions of the actual operations that can beperformed. The actual operations that correspond to these terms can varydepending on the particular implementation and are, based on thisdisclosure, readily discernible by one of ordinary skill in the art.

Disclosed embodiments of an expandable sheath can minimize trauma to thevessel by allowing for temporary expansion of a portion of theintroducer sheath to accommodate the delivery system, followed by areturn to the original diameter once the device passes through. Someembodiments can comprise a sheath with a smaller profile than that ofprior art introducer sheaths. Furthermore, present embodiments canreduce the length of time a procedure takes, as well as reduce the riskof a longitudinal or radial vessel tear, or plaque dislodgement becauseonly one sheath is required, rather than several different sizes ofsheaths. Embodiments of the present expandable sheath can avoid the needfor multiple insertions for the dilation of the vessel.

FIG. 1 illustrates a sheath 8 according to the present disclosure, inuse with a representative delivery apparatus 10, for delivering aprosthetic device 12, such as a tissue heart valve to a patient. Theapparatus 10 can include a steerable guide catheter 14 (also referred toas a flex catheter), a balloon catheter 16 extending through the guidecatheter 14, and a nose catheter 18 extending through the ballooncatheter 16. The guide catheter 14, the balloon catheter 16, and thenose catheter 18 in the illustrated embodiment are adapted to slidelongitudinally relative to each other to facilitate delivery andpositioning of the valve 12 at an implantation site in a patient's body,as described in detail below. Generally, sheath 8 is inserted into avessel, such as the transfemoral vessel, passing through the skin ofpatient, such that the distal end of the sheath 8 is inserted into thevessel. Sheath 8 can include a hemostasis valve at the opposite,proximal end of the sheath. The delivery apparatus 10 can be insertedinto the sheath 8, and the prosthetic device 12 can then be deliveredand implanted within patient.

FIGS. 2A, 2B, and 2D show section views of embodiments of a sheath 22for use with a delivery apparatus such as that shown in FIG. 1. FIG. 2Cshows a perspective view of one embodiment of an inner layer 24 for usewith the sheath 22. Sheath 22 includes an inner layer, such as innerpolymeric tubular layer 24, an outer layer, such as outer polymerictubular layer 26, and an intermediate tubular layer 28 disposed betweenthe inner and outer polymeric tubular layers 24, 26. The sheath 22defines a lumen 30 through which a delivery apparatus can travel into apatient's vessel in order to deliver, remove, repair, and/or replace aprosthetic device. Such introducer sheaths 22 can also be useful forother types of minimally invasive surgery, such as any surgery requiringintroduction of an apparatus into a subject's vessel. For example, thesheath 22 also can be used to introduce other types of deliveryapparatus for placing various types of intraluminal devices (e.g.,stents, stented grafts, etc.) into many types of vascular andnon-vascular body lumens (e.g., veins, arteries, esophagus, ducts of thebiliary tree, intestine, urethra, fallopian tube, other endocrine orexocrine ducts, etc.).

The outer polymeric tubular layer 26 and the inner polymeric tubularlayer 24 can comprise, for example, PTFE (e.g. Teflon®), polyimide,PEEK, polyurethane, nylon, polyethylene, polyamide, polyether blockamides (e.g. PEBAX®), polyether block ester copolymer, polyesters,fluoropolymers, polyvinyl chloride, thermoset silicone, latex,poly-isoprene rubbers, polyolefin, other medical grade polymers, orcombinations thereof. The intermediate tubular layer 28 can comprise ashape memory alloy such as Nitinol, and/or stainless steel, cobaltchromium, spectra fiber, polyethylene fiber, aramid fiber, orcombinations thereof.

The inner polymeric tubular layer 24 can advantageously be provided witha low coefficient of friction on its inner surface. For example, theinner polymeric tubular layer 24 can have a coefficient of friction ofless than about 0.1. Some embodiments of a sheath 22 can include alubricious liner on the inner surface 32 of the inner polymeric tubularlayer 24. Such a liner can facilitate passage of a delivery apparatusthrough the lumen 30 of the sheath 22. Examples of suitable lubriciousliners include materials that can reduce the coefficient of friction ofthe inner polymeric tubular layer 24, such as PTFE, polyethylene,polyvinylidine fluoride, and combinations thereof. Suitable materialsfor a lubricious liner also include other materials desirably having acoefficient of friction of about 0.1 or less.

The inner diameter of the intermediate tubular layer 28 varies dependingon the application and size of the delivery apparatus and prostheticdevice. In some embodiments, the inner diameter ranges from about 0.005inches to about 0.400 inches. The thickness of the intermediate tubularlayer 28 can be varied depending on the desired amount of radialexpansion, as well as the strength required. For example, the thicknessof the intermediate tubular layer 28 can be from about 0.002 inches toabout 0.025 inches. The thicknesses of the inner polymeric tubular layer24 and the outer polymeric tubular layer 26 can also be varied dependingon the particular application of the sheath 22. In some embodiments, thethickness of the inner polymeric tubular layer 24 ranges from about0.0005 inches to about 0.010 inches, and in one particular embodiment,the thickness is about 0.002 inches. Outer polymeric tubular layers 26can have a thickness of from about 0.002 inches to about 0.015 inches,and in one particular embodiment the outer polymeric tubular layer 26has a thickness of about 0.010 inches.

The hardness of each layer of the sheath 22 can also be varied dependingon the particular application and desired properties of the sheath 22.In some embodiments, the outer polymeric tubular layer 26 has a Shorehardness of from about 25 Durometer to about 75 Durometer.

Additionally, some embodiments of a sheath 22 can include an exteriorhydrophilic coating on the outer surface 34 of the outer polymerictubular layer 26. Such a hydrophilic coating can facilitate insertion ofthe sheath 22 into a patient's vessel. Examples of suitable hydrophiliccoatings include the Harmony™ Advanced Lubricity Coatings and otherAdvanced Hydrophilic Coatings available from SurModics, Inc., EdenPrairie, Minn. DSM medical coatings (available from Koninklijke DSMN.V., Heerlen, the Netherlands), as well as other hydrophilic coatings,are also suitable for use with the sheath 22.

In some embodiments, the outer surface 34 of the outer polymeric tubularlayer 26 can be modified. For example, surface modifications such asplasma etching can be performed on the outer surface 34. Similarly,other surfaces, both outer and inner, can be surface modified accordingto certain embodiments and desired application. In some embodiments,surface modification can improve adhesion between the layers in theareas of the modification.

The sheath 22 also can have at least one radiopaque filler or marker.The radiopaque filler or marker can be associated with the outer surface34 of the outer polymeric tubular layer 26. Alternatively, theradiopaque filler or marker can be embedded or blended within the outerpolymeric tubular layer 24. Similarly, the radiopaque filler or markercan be associated with a surface of the inner polymeric tubular layer 24or the intermediate tubular layer 28 or embedded within either or bothof those layers.

Suitable materials for use as a radiopaque filler or marker include, forexample, barium sulfite, bismuth trioxide, titanium dioxide, bismuthsubcarbonate, or combinations thereof. The radiopaque filler can bemixed with or embedded in the material used to form the outer polymerictubular layer 26, and can comprise from about 5% to about 45% by weightof the outer polymeric tubular layer. More or less radiopaque materialcan be used in some embodiments, depending on the particularapplication.

In some embodiments, the inner polymeric tubular layer 24 can comprise asubstantially uniform cylindrical tube. In alternative embodiments, theinner polymeric tubular layer 24 can have at least one section ofdiscontinuity along its longitudinal axis to facilitate radial expansionof the inner polymeric tubular layer 24. For example, the innerpolymeric tubular layer 24 can be provided with one or more longitudinalnotches and/or cuts 36 extending along at least a portion of the lengthof the sheath 22. Such notches or cuts 36 can facilitate radialexpansion of the inner polymeric tubular layer 24, thus accommodatingpassage of a delivery apparatus or other device. Such notches and/orcuts 36 can be provided near the inner surface 32, near the outersurface 37, and/or substantially through the entire thickness of theinner polymeric layer 24. In embodiments with a plurality of notchesand/or cuts 36, such notches and/or cuts 36 can be positioned such thatthey are substantially equally spaced from one another circumferentiallyaround the inner polymeric layer 24. Alternatively, notches and cuts 36can be spaced randomly in relation to one another, or in any otherdesired pattern. Some or all of any provided notches and/or cuts 36 canextend longitudinally along substantially the entire length of thesheath 22. Alternatively, some or all of any provided notches and/orcuts 36 can extend longitudinally only along a portion of the length ofthe sheath 22.

As shown in FIGS. 2B and 2C (which illustrates only the inner polymerictubular layer 24), in some embodiments, the inner polymeric tubularlayer 24 contains at least one notch or cut 36 that extendslongitudinally and parallel to an axis defined by the lumen 30,extending substantially the entire length of the sheath 22. Thus, uponintroduction of a delivery apparatus, the inner polymeric tubular layer24 can split open along the notch and/or cut 36 and expand, thusaccommodating the delivery apparatus.

Additionally or alternatively, as shown in FIG. 2D, the outer polymerictubular layer 26 can comprise one or more notches and/or cuts 36.Notches and/or cuts 36, in some embodiments, do not extend through theentire thickness of the outer tubular layer 26. The notches and/or cuts36 can be separable upon radial expansion of the sheath 22. The outerpolymeric tubular layer 26 can be retractable longitudinally, or able tobe pulled back away from the intermediate tubular layer 28 and the innerpolymeric tubular layer 24. In embodiments with a retractable outerpolymeric tubular layer 26, the outer polymeric tubular layer 26 can beretracted to accommodate or facilitate passage of a delivery apparatusthrough the lumen 30, and then can be replaced to its original positionon the sheath 22.

FIG. 3 illustrates an elevation view of the sheath 22 shown in FIG. 2A.In this view, only the outer polymeric tubular layer 26 is visible. Thesheath 22 comprises a proximal end 38 and a distal end 40 opposite theproximal end 38. The sheath 22 can include a hemostasis valve inside thelumen of the sheath 22, at or near the proximal end 38 of the sheath 22.Additionally, the sheath 22 can comprise a soft tip 42 at the distal end40 of the sheath 22. Such a soft tip 42 can be provided with a lowerhardness than the other portions of the sheath 22. In some embodiments,the soft tip 42 can have a Shore hardness from about 25 D to about 40 D.

As shown in FIG. 3, the unexpanded original outer diameter of the sheath22 can be substantially constant across the length of the sheath 22,substantially from the proximal end 38 to the distal end 40. Inalternative embodiments, such as the ones illustrated in FIGS. 4A-4B,the original unexpanded outer diameter of the sheath 22 can decreasefrom the proximal end 38 to the distal end 40. As shown in theembodiment in FIG. 4A, the original unexpanded outer diameter candecrease along a gradient, from the proximal end 38 to the distal end40. In alternative embodiments, such as the one shown in FIG. 4B, theoriginal unexpanded outer diameter of sheath 22 can incrementally stepdown along the length of the sheath 22, wherein the largest originalunexpanded outer diameter is near the proximal end 38 and the smallestoriginal unexpanded outer diameter is near the distal end 40 of thesheath 22.

As shown in FIGS. 5-6, the sheath 22 can be designed to locally expandas the prosthetic device is passed through the lumen of the sheath 22,and then substantially return to its original shape once the prostheticdevice has passed through that portion of the sheath 22. For example,FIG. 5 illustrates a sheath 22 have a localized bulge 44, representativeof a device being passed through the internal lumen of the sheath 22.FIG. 5 shows the device close to the proximal end 38 of the sheath 22,close to the area where the device is introduced into the sheath 22.FIG. 6 shows the sheath 22 of FIG. 5, with the device having progressedfurther along the sheath 22. The localized bulge 44 is now closer to thedistal end 40 of the sheath 22, and thus is about to be introduced to apatient's vessel. As evident from FIGS. 5 and 6, once the localizedbulge associated with the device has passed through a portion of thelumen of the sheath 22, that portion of the sheath 22 can automaticallyreturn to its original shape and size, at least in part due to thematerials and structure of the sheath 22.

The sheath 22 has an unexpanded inner diameter equal to the innerdiameter of the inner polymeric tubular layer (not visible in FIGS.5-6), and an unexpanded outer diameter 46 equal to the outer diameter ofthe outer polymeric tubular layer 26. The sheath 22 is designed to beexpanded to an expanded inner diameter and an expanded outer diameter 48which are larger than the unexpanded inner diameter and the unexpandedouter diameter 46, respectively. In one representative embodiment, theunexpanded inner diameter is about 16 Fr and the unexpanded outerdiameter 46 is about 19 Fr, while the expanded inner diameter is about26 Fr and the expanded outer diameter 48 is about 29 Fr. Differentsheaths 22 can be provided with different expanded and unexpanded innerand outer diameters, depending on the size requirements of the deliveryapparatus for various applications. Additionally, some embodiments canprovide more or less expansion depending on the particular designparameters, the materials, and/or configurations used.

In some embodiments of a sheath according to the present disclosure, andas shown in section in FIG. 7 and in elevation in FIG. 8, the sheath 22can additionally comprise an outer covering, such as outer polymericcovering 50, disposed on the outer surface 52 of the outer polymerictubular layer 26. The outer polymeric covering 50 can provide aprotective covering for the underlying sheath 22. In some embodiments,the outer polymeric covering 50 can contain a self-expandable sheath ina crimped or constrained state, and then release the self-expandablesheath upon removal of the outer polymeric covering 50. For example, insome embodiments of a self-expandable sheath, the intermediate layer 28can comprise Nitinol and/or other shape memory alloys, and theintermediate layer 28 can be crimped or radially compressed to a reduceddiameter within the outer polymeric tubular layer 26 and the outerpolymeric covering 50. Once the self-expandable sheath is at leastpartially inserted into a patient's vessel, the outer polymeric covering50 can be slid back, peeled away, or otherwise at least partiallyremoved from the sheath. To facilitate removal of the outer polymericcovering 50, a portion of the outer polymeric covering 50 can remainoutside the patient's vessel, and that portion can be pulled back orremoved from the sheath to allow the sheath to expand. In someembodiments, substantially the entire outer polymeric covering 50 can beinserted, along with the sheath, into a patient's vessel. In theseembodiments, an external mechanism attached to the outer polymericcovering 50 can be provided, such that the outer polymeric covering canbe at least partially removed from the sheath once the sheath isinserted into a patient's vessel.

Once no longer constrained by the outer polymeric covering 50, theradially compressed intermediate layer 28 can self-expand, causingexpansion of the sheath along the length of the intermediate layer 28.In some embodiments, portions of the sheath can radially collapse, atleast partially returning to the original crimped state, as the sheathis being withdrawn from the vessel after completion of the surgicalprocedure. In some embodiments, such collapse can be facilitated and/orencouraged by an additional device or layer that, in some embodiments,can be mounted onto a portion of the sheath prior to the sheath'sinsertion into the vessel.

The outer polymeric covering 50, in some embodiments, is not adhered tothe other layers of the sheath 22. For example, the outer polymericcovering 50 may be slidable with respect to the underlying sheath, suchthat it can be easily removed or retracted from its initial position onthe sheath 22.

As seen in FIG. 8, the outer polymeric covering 50 can include one ormore peel tabs 54 to facilitate manual removal of the outer polymericcovering 50. The outer polymeric covering 50 can be automatically ormanually retractable and/or splittable to facilitate radial expansion ofthe sheath 22. Peel tabs 54 can be located approximately 90 degrees fromany cut or notch present in the outer polymeric covering 50, andapproximately 180 degrees offset from one another. In alternativeembodiments, the peel tabs 54 can extend substantially around thecircumference of the outer polymeric covering 50, thus resulting in asingle circular peel tab 54.

Suitable materials for the outer polymeric covering 50 are similar tothose materials suitable for the inner polymeric tubular layer and theouter polymeric tubular layer, and can include PTFE and/or high densitypolyethylene.

Turning now to the intermediate tubular layer 28, several differentconfigurations are possible. The intermediate tubular layer 28 isgenerally a thin, hollow, substantially cylindrical tube comprising anarrangement, pattern, structure, or configuration of wires or struts,however other geometries can also be used. The intermediate tubularlayer 28 can extend along substantially the entire length of the sheath22, or alternatively, can extend only along a portion of the length ofsheath 22. Suitable wires can be round, ranging from about 0.0005 inchesthick to about 0.10 inches thick, or flat, ranging from about 0.0005inches×0.003 inches to about 0.003 inches×0.007 inches. However, othergeometries and sizes are also suitable for certain embodiments. Ifbraided wire is used, the braid density can be varied. Some embodimentshave a braid density of from about thirty picks per inch to about eightypicks per inch and can include up to thirty-two wires in various braidpatterns.

One representative embodiment of an intermediate tubular layer comprisesa braided Nitinol composite which is at least partially encapsulated byan inner polymeric tubular member and an outer polymeric tubular memberdisposed on inner and outer surfaces of the intermediate tubular layer,respectively. Such encapsulation by polymeric layers can be accomplishedby, for example, fusing the polymeric layers to the intermediate tubularlayer, or dip coating the intermediate tubular layer. In someembodiments, an inner polymeric tubular member, an intermediate tubularlayer, and an outer polymeric tubular layer can be arranged on amandrel, and the layers can then be thermally fused or melted into oneanother by placing the assembly in an oven or otherwise heating it. Themandrel can then be removed from the resulting sheath. In otherembodiments, dip coating can be used to apply an inner polymeric tubularmember to the surface of a mandrel. The intermediate tubular layer canthen be applied, and the inner polymeric tubular member allowed to cure.The assembly can then be dip coated again, such as to apply a thincoating of, for example, polyurethane, which will become the outerpolymeric tubular member of the sheath. The sheath can then be removedfrom the mandrel.

Additionally, the intermediate tubular layer 28 can be, for example,braided or laser cut to form a pattern or structure, such that theintermediate tubular layer 28 is amenable to radial expansion. FIGS.9-23 illustrate partial elevation views of various structures for theintermediate tubular layer. Some illustrated structures, such as thoseshown in FIGS. 11-14 and 23, include at least one discontinuity. Forexample, the struts 56, 58, 60, 62, 64 shown in FIGS. 11, 12, 13, 14,and 23, respectively, result in a discontinuous intermediate tubularlayer 28 in that the struts 56, 58, 60, 62, 64 separate adjacentsections of the intermediate tubular layer 28 from each other, where thesections are spaced apart from each other along a longitudinal axisparallel to the lumen of the sheath. Thus, the structure of theintermediate tubular layer 28 can vary from section to section, changingalong the length of the sheath.

The structures shown in FIGS. 9-23 are not necessarily drawn to scale.Components and elements of the structures can be used alone or incombination within a single intermediate tubular layer 28. The scope ofthe intermediate tubular layer 28 is not meant to be limited to theseparticular structures; they are merely exemplary embodiments.

Alternative embodiments of a sheath for introducing a prosthetic deviceare also described. For example, FIGS. 24-26 illustrate a section viewand a perspective view, respectively, of a sheath 66 for introducing aprosthetic device into a body. The sheath 66 comprises an inner layer,such as inner polymeric layer 68, an outer layer, such as polymerictubular layer 70, and a hemostasis valve (not shown). The innerpolymeric layer 68 and the outer polymeric tubular layer 70 at leastpartially enclose a lumen 72, through which a delivery apparatus andprosthetic device can pass from outside the patient's body into thepatient's vessel. Either or both of the inner polymeric layer 68 and theouter polymeric layer 70 can be provided with at least one longitudinalnotch and/or cut to facilitate radial expansion of the sheath.

For example, FIG. 24 illustrates a longitudinal notch 74 in the innerpolymeric layer 68 that can facilitate radial expansion of the sheath66. The longitudinal notch 74 can separate or split open completely uponapplication of a radial force due to insertion of a delivery apparatusor prosthetic device. Similarly, FIG. 25 illustrates a longitudinal cut76 in the inner polymeric layer 68 that can also facilitate radialexpansion of the sheath 66. The outer polymeric layer 70 can,additionally or alternatively, comprise one or more longitudinal cuts 76or notches 74. Such cuts and/or notches, whether in the inner polymericlayer 68 or the outer polymeric layer 70, can extend substantiallythrough the entire thickness of the layer, or can extend only partiallythrough the thickness of the layer. The cuts and/or notches can bepositioned at or near the inner or outer surface, or both surfaces, ofthe inner and/or outer polymeric layers 68,70.

FIG. 26 illustrates a perspective view of one embodiment of an innerpolymeric layer 68 with longitudinal notches 74 and a longitudinal cut76. More or fewer notches 74 and/or cuts 76 can be provided. Forclarity, the outer polymeric layer 70 is not shown in FIG. 26. As shownin FIG. 26, longitudinal notches 74 and/or cuts 76 can extend only alonga portion of the length of sheath 66. In alternative embodiments, one ormore notches 74 and/or cuts 76 can extend substantially along the entirelength of the sheath 66. Additionally, notches 74 and/or cuts 76 can bepositioned randomly or patterned.

One particular embodiment of a sheath 66 comprises a sheath having anotch or cut in the outer polymeric layer 70 or the inner polymericlayer 68 that extends longitudinally along approximately 75% of thelength of the sheath 66. If such a notch or cut extends only partiallythrough the associated layer, it can have a relatively low tear force,such as a tear force of about 0.5 lbs, so that the notch splits openrelatively easily during use.

The inner polymeric layer 68 and the outer polymeric layer 70 canoptionally be adhered together or otherwise physically associated withone another. The amount of adhesion between the inner polymeric layer 68and the outer polymeric layer 70 can be variable over the surfaces ofthe layers. For example, little to no adhesion can be present at areasaround or near any notches and/or cuts present in the layers, so as notto hinder radial expansion of the sheath 66. Adhesion between the layerscan be created by, for example, thermal bonding and/or coatings.Embodiments of a sheath 66 can be formed from an extruded tube, whichcan serve as the inner polymeric layer 68. The inner polymeric layer 68can be surface treated, such as by plasma etching, chemical etching orother suitable methods of surface treatment. By treating the surface ofthe inner polymeric layer 68, the outer surface of the inner polymericlayer 68 can have areas with altered surface angles that can providebetter adhesion between the inner polymeric layer 68 and the outerpolymeric layer 70. The treated inner polymeric layer can be dip coatedin, for example, a polyurethane solution to form the outer polymericlayer 70. In some configurations, the polyurethane may not adhere wellto untreated surface areas of the inner polymeric layer 68. Thus, bysurface treating only surface areas of the inner polymeric layer 68 thatare spaced away from the areas of expansion (e.g. the portion of theinner polymeric layer 68 near notches 74 and/or cuts 76), the outerpolymeric layer 70 can be adhered to some areas of the inner polymericlayer 68, while other areas of the inner polymeric layer 68 remain freeto slide relative to the outer polymeric layer 70, thus allowing forexpansion of the diameter of the sheath 66. Thus, areas around or nearany notches 74 and/or cuts 76 can experience little to no adhesionbetween the layers, while other areas of the inner and outer polymericlayers 68, 70 can be adhesively secured or otherwise physicallyassociated with each other.

As with previously disclosed embodiments, the embodiments illustrated inFIGS. 24-26 can be applied to sheaths having a wide variety of inner andouter diameters. Applications can utilize a sheath of the presentdisclosure with an inner diameter of the inner polymeric layer 68 thatis expandable to an expanded diameter of from about 3 Fr to about 26 Fr.The expanded diameter can vary slightly along the length of the sheath66. For example, the expanded outer diameter at the proximal end of thesheath 66 can range from about 3 Fr to about 28 Fr, while the expandedouter diameter at the distal end of the sheath 66 can range from about 3Fr to about 25 Fr. Embodiments of a sheath 66 can expand to an expandedouter diameter that is from about 10% greater than the originalunexpanded outer diameter to about 100% greater than the originalunexpanded outer diameter.

In some embodiments, the outer diameter of the sheath 66 graduallydecreases from the proximal end of the sheath 66 to the distal end ofthe sheath 66. For example, in one embodiment, the outer diameter cangradually decrease from about 26 Fr at the proximal end to about 18 Frat the distal end. The diameter of the sheath 66 can transitiongradually across substantially the entire length of the sheath 66. Inother embodiments, the transition or reduction of the diameter of thesheath 66 can occur only along a portion of the length of the sheath 66.For example, the transition can occur along a length from the proximalend to the distal end, where the length can range from about 0.5 inchesto about the entire length of sheath 66.

Suitable materials for the inner polymeric layer 68 can have a highelastic strength and include materials discussed in connection withother embodiments, especially Teflon (PTFE), polyethylene (e.g. highdensity polyethylene), fluoropolymers, or combinations thereof. In someembodiments, the inner polymeric layer 68 preferably has a lowcoefficient of friction, such as a coefficient of friction of from about0.01 to about 0.5. Some preferred embodiments of a sheath 66 comprise aninner polymeric layer 68 having a coefficient of friction of about 0.1or less.

Likewise, suitable materials for the outer polymeric layer 70 includematerials discussed in connection with other embodiments, and otherthermoplastic elastomers and/or highly elastic materials.

The Shore hardness of the outer polymeric layer 70 can be varied fordifferent applications and embodiments. Some embodiments include anouter polymeric layer with a Shore hardness of from about 25A to about80A, or from about 20D to about 40D. One particular embodiment comprisesa readily available polyurethane with a Shore hardness of 72A. Anotherparticular embodiment comprises a polyethylene inner polymeric layerdipped in polyurethane or silicone to create the outer polymeric layer.

The sheath 66 can also include a radiopaque filler or marker asdescribed above. In some embodiments, a distinct radiopaque marker orband can be applied to some portion of the sheath 66. For example, aradiopaque marker can be coupled to the inner polymeric layer 68, theouter polymeric layer 70, and/or can be positioned in between the innerand outer polymeric layers 68, 70.

FIGS. 27A-27E and 28 illustrate section views of various embodiments ofunexpanded (FIGS. 27A-27E) and expanded (FIG. 28) sheaths 66 accordingto the present disclosure. The sheath 66 includes a split outerpolymeric tubular layer 70 having a longitudinal cut 76 through thethickness of the outer polymeric tubular layer 70 such that the outerpolymeric tubular layer 70 comprises a first portion 78 and a secondportion 80 separable from one another along the cut 76. An expandableinner polymeric layer 68 is associated with an inner surface 82 of theouter polymeric tubular layer 70, and, in the unexpanded configurationshown in FIG. 27, a portion of the inner polymeric layer 68 extendsthrough a gap created by the cut 76 and can be compressed between thefirst and second portions 78, 80 of the outer polymeric tubular layer70. Upon expansion of the sheath 66, as shown in FIG. 28, first andsecond portions 78, 80 of the outer polymeric tubular layer 70 haveseparated from one another, and the inner polymeric layer 68 is expandedto a substantially cylindrical tube. In some embodiments, two or morelongitudinal cuts 76 may be provided through the thickness of the outerpolymeric tubular layer 70. In such embodiments, a portion of the innerpolymeric layer 68 may extend through each of the longitudinal cuts 76provided in the outer polymeric tubular layer 70.

Preferably, the inner polymeric layer 68 comprises one or more materialsthat are elastic and amenable to folding and/or pleating. For example,FIG. 27A illustrates an inner polymeric layer 68 with folded regions 85.As seen in FIGS. 27A-27E, the sheath 66 can be provided with one or morefolded regions 85. Such folded regions 85 can be provided along a radialdirection and substantially conform to the circumference of the outerpolymeric tubular layer 70. At least a portion of the folded regions 85can be positioned adjacent the outer surface 83 of the outer polymerictubular layer 70. Additionally, as shown in FIGS. 27B and 27E, at leasta portion of the folded region or regions 85 can be overlapped by anouter covering, such as outer polymeric covering 81. The outer polymericcovering 81 can be adjacent at least a portion of the outer surface 83of the outer polymeric tubular layer 70. The outer polymeric covering 81serves to at least partially contain the folded regions 85 of the innerpolymeric layer 68, and can also prevent the folded regions 85 fromseparating from the outer polymeric tubular layer 70 when, for example,the sheath 66 undergoes bending. In some embodiments, the outerpolymeric covering 81 can be at least partially adhered to the outersurface 83 of the outer polymeric tubular layer 70. The outer polymericcovering 81 can also increase the stiffness and/or durability of thesheath 66. Additionally, as shown in FIGS. 27B and 27E, the outerpolymeric covering 81 may not entirely overlap the circumference of thesheath 66. For example, the outer polymeric covering 81 may be providedwith first and second ends, where the ends do not contact one another.In these embodiments, only a portion of the folded region 85 of theinner polymeric layer 68 is overlapped by the outer polymeric covering81.

In embodiments having a plurality of folded regions 85, the regions canbe equally displaced from each other around the circumference of theouter polymeric tubular layer 70. Alternatively, the folded regions canbe off-center, different sizes, and/or randomly spaced apart from eachother. While portions of the inner polymeric layer 68 and the outertubular layer 70 can be adhered or otherwise coupled to one another, thefolded regions 85 preferably are not adhered or coupled to the outertubular layer 70. For example, adhesion between the inner polymericlayer 68 and the outer tubular layer 70 can be highest in areas ofminimal expansion.

One particular embodiment of the sheath illustrated in FIGS. 27-28comprises a polyethylene (e.g. high density polyethylene) outerpolymeric tubular layer 70 and a PTFE inner polymeric layer 68. However,other materials are suitable for each layer, as described above.Generally, suitable materials for use with the outer polymeric tubularlayer 70 include materials having a high stiffness or modulus ofstrength that can support expansion and contraction of the innerpolymeric layer 68.

In some embodiments, the outer polymeric tubular layer 70 comprises thesame material or combination of materials along the entire length of theouter polymeric tubular layer 70. In alternative embodiments, thematerial composition can change along the length of the outer polymerictubular layer 70. For example, the outer polymeric tubular layer can beprovided with one or more segments, where the composition changes fromsegment to segment. In one particular embodiment, the Durometer ratingof the composition changes along the length of the outer polymerictubular layer 70 such that segments near the proximal end comprise astiffer material or combination of materials, while segments near thedistal end comprise a softer material or combination of materials. Thiscan allow for a sheath 66 having a relatively stiff proximal end at thepoint of introducing a delivery apparatus, while still having arelatively soft distal tip at the point of entry into the patient'svessel.

As with other disclosed embodiments, the embodiments of sheath 66 shownin FIGS. 27-28 can be provided in a wide range of sizes and dimensions.For example, the sheath 66 can be provided with an unexpanded innerdiameter of from about 3 Fr to about 26 Fr. In some embodiments, thesheath 66 has an unexpanded inner diameter of from about 15 Fr to about16 Fr. In some embodiments, the unexpanded inner diameter of the sheath66 can range from about 3 Fr to about 26 Fr at or near the distal end ofsheath 66, while the unexpanded inner diameter of the sheath 66 canrange from about 3 Fr to about 28 Fr at or near the proximal end ofsheath 66. For example, in one unexpanded embodiment, the sheath 66 cantransition from an unexpanded inner diameter of about 16 Fr at or nearthe distal end of the sheath 66 to an unexpanded inner diameter of about26 Fr at or near the proximal end of the sheath 66.

The sheath 66 can be provided with an unexpanded outer diameter of fromabout 3 Fr to about 30 Fr, and, in some embodiments has an unexpandedouter diameter of from about 18 Fr to about 19 Fr. In some embodiments,the unexpanded outer diameter of the sheath 66 can range from about 3 Frto about 28 Fr at or near the distal end of sheath 66, while theunexpanded outer diameter of the sheath 66 can range from about 3 Fr toabout 30 Fr at or near the proximal end of sheath 66. For example, inone unexpanded embodiment, the sheath 66 can transition from anunexpanded outer diameter of about 18 Fr at or near the distal end ofthe sheath 66 to an unexpanded outer diameter of about 28 Fr at or nearthe proximal end of the sheath 66.

The thickness of the inner polymeric layer 68 can vary, but in somepreferred embodiments is from about 0.002 inches to about 0.015 inches.In some embodiments, expansion of the sheath 66 can result in expansionof the unexpanded outer diameter of from about 10% or less to about 430%or more.

As with other illustrated and described embodiments, the embodimentsshown in FIGS. 27-28 can be provided with a radiopaque filler and/or aradiopaque tip marker as described above. The sheath 66 can be providedwith a radiopaque tip marker provided at or near the distal tip of thesheath 66. Such a radiopaque tip marker can comprise materials such asthose suitable for the radiopaque filler, platinum, iridium,platinum/iridium alloys, stainless steel, other biocompatible metals, orcombinations thereof.

FIGS. 29A-29D show section views of other possible configurations of asheath 66 for introducing a prosthetic device into a patient'svasculature. The sheath 66 comprises a polymeric tubular layer 84 havingan inner surface 86 and an outer surface 88. The thickness of thepolymeric tubular layer 84 extends from the inner surface 86 to theouter surface 88. As shown in FIGS. 29B-29D, the polymeric tubular layer84 can be formed with at least a first angular portion 90 of reducedthickness adjacent the inner surface 86 and a second angular portion 92of reduced thickness adjacent the outer surface 88, with the secondportion 92 at least partially overlapping the first portion 90. FIG. 29Aillustrates a similar configuration, where a second portion 92 at leastpartially overlaps a first portion 90 in a partial coil configuration.In the embodiment of FIG. 29A, the second portion 92 and the firstportion 90 can have the same thickness.

In preferred embodiments, the first and second portions 90, 92 are notadhered to one another. In some embodiments, and best seen in FIG. 29A,there can be a small gap 94 between the first and second portions 90, 92that can give the sheath 66 the appearance of having two interior lumens72, 94. FIGS. 29A-29D illustrate the sheath 66 in unexpandedconfigurations. Preferably, upon expansion of the sheath 66, the ends ofthe first and second portions 90, 92 abut or are in close proximity toeach other to reduce or eliminate any gap between them.

In some embodiments, a sheath 66 can comprise a partial slit or scoreline along at least a portion of its length. For example, as shown inFIG. 33, a sheath 66 can comprise an outer polymeric tubular layer 70over an inner polymeric layer 68. The inner polymeric layer can extendthrough a cut in the outer polymeric tubular layer 70, to form a foldedregion 85 on the outer surface of the outer polymeric tubular layer 70,such as also shown in FIG. 27C. The folded region 85 of the inner layer,in some embodiments, terminates before the outer polymeric tubular layer70 (i.e. the outer polymeric tubular layer 70 is longer than the innerlayer). As shown in FIG. 33, in these embodiments, the sheath 66 cancomprise a partial slit or score line 77 that can extend from thetermination (distal end) 75 of the folded region 85 to the distal end 40of the sheath 66. In some embodiments, score line 77 can facilitateexpansion of the sheath 66.

Score line 77 can be substantially centrally located with respect to thefolded region 85. In alternative embodiments, score line 77 can bepositioned in other locations relative to the folded region 85. Also,sheath 66 can comprise one or more score lines 77. For example, as shownin FIG. 34, one or more score lines 77 can be peripherally located withrespect to the folded region 85. The one or more score lines 77 can bepositioned anywhere around the circumference of the outer polymerictubular layer 70. In embodiments comprising a radiopaque marker 69 asseen in FIG. 33, a score line 77 can extend from, for example, thedistal end of the radiopaque marker 69 substantially to the distal end40 of the sheath 66.

Various methods can be used to produce the sheaths discussed above andbelow, throughout the present disclosure. For example, a method ofmaking the sheath shown in FIGS. 2A-2D can comprise providing a mandreland applying an inner layer on the mandrel, such as by spray coating ordip coating the mandrel. An intermediate layer, such as a meshstructure, can then be mounted on the inner layer. An outer layer can beapplied over the intermediate layer, such as by a second spray coatingor dip coating step. Methods can comprise etching or surface treating atleast a portion of the inner layer. Also, methods can comprise providingone or more notches and/or cuts in the inner layer and/or the outerlayer. Cuts and/or notches can be provided by, for example, lasercutting or etching one or more layers.

In some embodiments of methods of making a sheath such as the sheathsillustrated in FIGS. 2A-2D, layers can be pre-formed and mounted on amandrel, and then fused or thermally bonded together. For example, inone method, an inner layer is applied to a mandrel. An intermediatelayer can be applied to the outer surface of the inner layer. An outerlayer can be applied to the outer surface of the intermediate layer.Heat shrink tubing can be applied, and the assembly heated, such thatthe inner layer, the intermediate layer, and/or the outer layer arethermally bonded and compressed together under the heat shrink tubing.

FIG. 30 illustrates a block diagram of one method of producing a sheathfor use with a delivery apparatus in minimally invasive surgery. One ormore mandrels can be provided (step 100). The mandrel can be providedwith an exterior coating, such as a Teflon® coating, and the mandrel'sdiameter can be predetermined, based on the desired size of theresulting sheath. A liner that will become the inner polymeric layer ofthe sheath, such as a PTFE or high density polyethylene liner, can bemounted on the mandrel (step 102). The liner can be etched and/orsurface treated prior to being mounted on the mandrel, according toconventional etching and surface treatment methods. FIG. 32A illustratesa section view of a sheath at steps 100 and 102 of FIG. 30. A coatedmandrel 96 is inserted within the lumen 72 of the inner polymeric layer68. The circumference of the inner polymeric layer 68 is larger than thecircumference of the mandrel 96, such that an excess portion of theinner polymeric layer 68 can be gathered above the mandrel 96.

A layer of material that will become the outer polymeric tubular layer,such as a layer comprising polyurethane or polyolefin, can be cut ornotched through all, substantially all, or a part of the thickness ofthe layer (step 104). Such a cut or notch can extend longitudinallyalong the length of the layer and can extend along substantially theentire length of the outer polymeric tubular layer. In alternativeembodiments, the cut or notch can be provided along only a portion ofthe outer polymeric tubular layer. For example, the outer polymerictubular layer can be cut starting at the distal end of the outerpolymeric tubular layer, with the cut ending before the proximal end ofthe outer polymeric tubular layer. In one embodiment, the cut can end ata transition, where the outer diameter of the outer polymeric tubularlayer increases or decreases. In one specific embodiment, the cut ornotch can extend longitudinally along about 75% of the length of thesheath.

The cut or notched outer polymeric tubular layer can be applied,positioned, adhered, mounted, thermally fused or bonded, dip coated,and/or otherwise coupled to the etched inner liner (step 106). FIG. 32Bshows a section view of the sheath at step 106 of FIG. 30, with outerpolymeric tubular layer 70 applied to the inner polymeric layer 68 suchthat a portion of the inner polymeric layer 68 extends between the cutformed between first and second portions 78, 80 of the outer polymerictubular layer 70.

In alternative embodiments, the outer polymeric tubular layer can benotched or cut after being mounted on the inner liner/mandrel assembly.The outer polymeric tubular layer can optionally be provided with ahydrophilic coating and/or provided with additional layers, such asbeing dip coated with polyurethane. Some portion of the inner liner canprotrude through the cut in the outer polymeric tubular layer after suchouter polymeric tubular layer is mounted onto the inner liner/mandrelarrangement. Using, for example, a split tool, the protruding portion ofthe inner liner can be folded down onto the outer surface of the outerpolymeric tubular layer (step 108). In some embodiments, the protrudingportion of the inner liner is folded down along the entire length of theresulting sheath, while in other embodiments, the protruding portion ofthe inner liner is only present along a portion of the length of thesheath, or is only folded down along a portion of the length of theresulting sheath. FIG. 32C shows a section view of the sheath at step108 of FIG. 30. A split tool 98 is used to fold the excess portion ofinner polymeric layer 68 over a portion of the outer surface 83 of theouter polymeric tubular layer 70. FIG. 32D shows a section view of thesheath after completion of step 108 of FIG. 30. Split tool 98 has beenremoved, and folding of the excess portion of the inner polymeric layer68 has been completed. FIG. 32E shows a section view of an outercovering, such as outer polymeric covering 99, that can be applied suchthat it overlaps a portion of the folded portion of inner polymericlayer 68. The outer polymeric covering 99 contacts at least a portion ofthe outer surface 83 of the outer polymeric tubular layer 70.

A soft, atraumatic tip can be provided at the distal end of theresulting sheath (step 110). Additional outer layers can also beapplied, if desired. Then, a layer of heat shrink tubing, such asfluorinated ethylene propylene (FEP) heat shrink tubing, can bepositioned over the entire assembly (step 112). An appropriate amount ofheat is applied, thus shrinking the heat shrink tubing and compressingthe layers of the sheath together, such that components of the sheathcan be thermally bonded or fused together where desired. Once thecomponents of the sheath have been bonded together, the heat shrinktubing can be removed (step 114). Finally, the proximal end of thesheath can be adhered or otherwise attached to a housing of a catheterassembly, and the sheath can be removed from the mandrel (step 116).

FIG. 31 illustrates a block diagram of an alternative embodiment of amethod of making a sheath. An inner liner, such as an etched PTFE tubingcan be applied to a tapered mandrel, such as a 16 Fr tapered mandrel,and trimmed to an appropriate length (step 200). A second mandrel, suchas a 0.070 inches diameter mandrel, can be inserted in the lumen of theinner liner such that the mandrels are arranged side by side in theinner liner (step 202). FIG. 32F shows a section view of a sheath atsteps 200 and 202 of FIG. 31. An inner liner or inner polymeric layer 68is applied on a first, tapered, mandrel 96. A second mandrel 97 isinserted into the lumen 72 of the inner polymeric layer 68 created bythe excess portion of the inner polymeric layer 68, as described.

A notched or cut outer polymeric tubular layer, such as high densitypolyethylene tubing that has been notched or cut longitudinally, can beslid onto the tapered mandrel and a portion of the inner liner, startingat the distal end of the tapered mandrel (step 204). The second mandrelcan then be removed (step 206). FIG. 32G illustrates a perspective viewof the sheath at steps 204 and 206 of FIG. 31. A polymeric outer tubularlayer 70 having a longitudinal cut is applied over the tapered mandrel96 and inner polymeric layer 68. The outer tubular layer conforms to theportion of the inner polymeric layer around the tapered mandrel 96, andthe portion of the inner polymeric layer 68 around the second mandrel 97extends through the longitudinal cut in the outer polymeric tubularlayer 70.

A split tool can be inserted into the portion of the lumen of the innerliner that was previously occupied by the second mandrel (step 208). Thesplit tool can then be used to form folds and/or pleats in the excessportion of the inner liner which now extends through the longitudinalcut in the outer polymeric tubular layer (step 210). A radiopaque markerband can optionally be applied at the distal end of the sheath (step212). Heat shrink tubing, such as FEP heat shrink tubing, can be appliedover the entire sheath, and heat can be applied to compress thecomponents of the sheath and bond or fuse them together (step 214). Thesplit tool, heat shrink tubing, and second mandrel can then be removed(step 216). The sheath can then be utilized with a delivery apparatus,such as by bonding the proximal end of the sheath to a polycarbonatehousing of a delivery apparatus or catheter assembly (step 218).

FIG. 32H illustrates an elevation view of the sheath at step 218 of FIG.31. The sheath 66, made according to described methods and processes,can be attached or bonded to a housing 101, such as by bonding theproximal end of the sheath 66 to the polycarbonate housing 101.

Sheaths of the present disclosure can be used with various methods ofintroducing a prosthetic device into a patient's vasculature. One suchmethod comprises positioning an expandable introducer sheath in apatient's vessel, passing a device through the introducer sheath, whichcauses a portion of the introducer sheath surrounding the device toexpand and accommodate the profile of the device, and automaticallyretracting the expanded portion of the introducer sheath to its originalsize after the device has passed through the expanded portion.

Some specific methods comprise delivering a tissue heart valve to apatient. Such methods can additionally comprise placing the tissue heartvalve in a crimped state on the distal end portion of an elongateddelivery apparatus, and inserting the elongated delivery device with thecrimped valve into the introducer sheath. Next, the delivery apparatuscan be advanced through the patient's vasculature to the treatment site,where the valve can be implanted.

In view of the many possible embodiments to which the principles of thedisclosed invention can be applied, it should be recognized that theillustrated embodiments are only preferred examples of the invention andshould not be taken as limiting the scope of the invention. Rather, thescope of the invention is defined by the following claims. We thereforeclaim as our invention all that comes within the scope and spirit ofthese claims.

What is claimed is:
 1. An introducer sheath comprising: a radiallyunexpanded configuration and a radially expanded configuration; an outertubular layer comprising an inner surface, an outer surface, and alongitudinal cut therethrough, the longitudinal cut defining a gap, thelongitudinal cut facilitating conversion of the introducer sheathbetween the radially unexpanded configuration and the radially expandedconfiguration, the outer tubular layer comprising high densitypolyethylene; a substantially circumferentially continuous inner tubularlayer comprising at least one longitudinal pleat, the at least onelongitudinal pleat extending through the gap to the outer surface of theouter tubular layer in the radially unexpanded configuration, the innertubular layer comprising PTFE; and a lumen enclosed by the inner tubularlayer and the outer tubular layer, wherein portions of the inner tubularlayer are adhered to portions of the inner surface of the outer tubularlayer, wherein the longitudinal pleat of the inner tubular layer is notadhered to the outer surface of the outer tubular layer, wherein aportion of the introducer sheath surrounding a device passing throughthe lumen thereof expands from the radially unexpanded configuration tothe radially expanded configuration to accommodate a profile of thedevice, and wherein the expanded portion of the sheath automaticallycontracts from the radially expanded configuration to the radiallyunexpanded configuration after the device passes therethrough.
 2. Theintroducer sheath of claim 1, further comprising an outer polymericcovering disposed over at least a portion of the outer surface of theouter polymeric layer.
 3. An introducer sheath comprising: a radiallyunexpanded configuration and a radially expanded configuration; an outertubular layer comprising an inner surface, an outer surface, and alongitudinal cut therethrough, the longitudinal cut defining a firstlongitudinal edge, a second longitudinal edge, and a gap therebetween,the longitudinal cut facilitating conversion of the introducer sheathbetween the radially unexpanded configuration and the radially expandedconfiguration; a substantially circumferentially continuous innertubular layer comprising at least one longitudinal pleat, the at leastone longitudinal pleat extending through the gap to the outer surface ofthe outer tubular layer in the radially unexpanded configuration; and alumen enclosed by the inner tubular layer and the outer tubular layer,wherein portions of the inner tubular layer are adhered to portions ofthe inner surface of the outer tubular layer, wherein the longitudinalpleat of the inner tubular layer is not adhered to the outer surface ofthe outer tubular layer, wherein a portion of the introducer sheathsurrounding a device passing through the lumen thereof expands from theradially unexpanded configuration to the radially expanded configurationto accommodate a profile of the device, and wherein the expanded portionof the sheath automatically contracts from the radially expandedconfiguration to the radially unexpanded configuration after the devicepasses therethrough.
 4. The introducer sheath of claim 3, wherein theouter tubular layer comprises at least one of polyethylene, high densitypolyethylene, or polyurethane.
 5. The introducer sheath of claim 3,wherein the inner tubular layer comprises PTFE.
 6. The introducer sheathof claim 3, wherein at least a portion of an outer surface of the innertubular layer is surface treated.
 7. The introducer sheath of claim 3,further comprising an outer polymeric covering disposed over at least aportion of the outer surface of the outer polymeric layer.
 8. Theintroducer sheath of claim 7, wherein the outer polymeric coveringcomprises polyurethane.
 9. The introducer sheath of claim 3, whereinportions of the inner tubular layer are adhered to portions of the innersurface of the outer tubular layer by thermal bonding.
 10. Theintroducer sheath of claim 3, wherein an expanded outer diameter of adistal end of the introducer sheath is from about 3 Fr to about 25 Fr.11. The introducer sheath of claim 3, wherein an expanded outer diameterof the introducer sheath is from about 10% to about 100% greater than anunexpanded outer diameter of the introducer sheath.
 12. The introducersheath of claim 3, further comprising a lubricating liner on at least aportion of an inner surface of the inner tubular layer.
 13. Theintroducer sheath of claim 3, further comprising a hydrophilic coatingon at least a portion of the outer surface of the outer tubular layer.14. The sheath of claim 3, wherein the first longitudinal edge of theouter tubular layer at least partially overlaps the second longitudinaledge of the outer tubular layer.
 15. The sheath of claim 3, wherein atleast a portion of the first longitudinal edge of the outer tubularlayer is thinner relative to a non-longitudinal-edge portion of theouter tubular layer.
 16. The sheath of claim 15, wherein at least aportion of the second longitudinal edge of the outer tubular layer isthinner relative to the non-longitudinal-edge portion of the outertubular layer.
 17. The sheath of claim 3, further comprising ahemostasis valve at or near a proximal end of the introducer sheath. 18.The sheath of claim 3, further comprising an atraumatic tip at a distalend of the introducer sheath.